1. Field of the Invention
The present invention relates generally to medical methods and devices. In particular, the present invention relates to methods and devices for applying energy to ablate, cut, drill, or otherwise modify soft or hard tissues.
Both water jet technology and laser technology have been proposed for various tissue cutting and modification protocols. While each of these approaches has achieved commercial success, neither is ideally suited for all tissue modification protocols. For example, water jet or stream cutting alone does not cauterize tissue and therefore cannot prevent excessive bleeding. Furthermore, it can require very high pressure water delivery systems which can be difficult to control. Similarly, the use of lasers for modifying tissue can require very high energies, which can only be generated with large high power and expensive laser equipment. While laser technology can be effectively applied to cauterize tissue and stop bleeding, an extensive tissue zone of thermal damage is unavoidable. The consequences are the formation of edema and swelling of the treated tissue. With prostate tissue for example, tissue edema and swelling may result with the patient going into urinary retention requiring catheterization. Thus, improved energy-based methods and devices for ablating, cutting, drilling, and otherwise modifying tissues, would be desirable.
A number of medical conditions affect the male urethra causing a variety of symptoms including painful or difficult urination, a swollen prostate, blood in the urine, lower back pain, and the like. Some of these conditions, such as prostatitis, are bacterial infections which can be treated with antibiotics and other drugs. Other conditions, however, such as benign prostatic hyperplasia (BPH) and prostatic carcinoma, result in enlargement of the prostate and obstruction of the urethra, sometimes leading to complete loss of bladder function.
Both BPH and prostatic cancer require treatments which remove, resect, or shrink tissue in the prostate surrounding the urethra. Common treatments include transurethral resection of the prostate (TURP) where a resectoscope is placed in the urethra and used to remove excess prostatic tissue. Another procedure, referred to as transurethral incision of the prostate (TUIP), relies on cutting muscle adjacent to the prostate to relax the bladder opening to relieve difficulty in urination. More recently, a procedure referred to as transurethral needle ablation (TUNA) has been introduced where a needle is advanced through the urethra into the prostate and used to deliver energy, such as microwave, radiofrequency, or ultrasound energy, to shrink the size of the prostate, again relieving pressure on the urethra. Laser resection or ablation using transurethral optical fibers also finds use.
One minimally invasive laser resection protocol is photoselective vaporization of the prostate (PVP) where a laser beam with output powers ranging from 60 to 120 W is directed from the urethra against prostatic tissue to achieve irradiance (power density) levels over a certain volumetric power density, referred to as a vaporization threshold, below which tissue coagulation rather than vaporization occurs. As the irradiance level increases above the vaporization threshold, tissue vaporization increases and coagulation decreases. Lasers, even those having the highest possible beam quality, produce divergent beams. Therefore, the laser spot size enlarges with increasing probe distance from the tissue, and the power density decreases. reducing the rate of vaporization. Hence, in order to maximize the rate of tissue vaporization and thereby limit the extent of the zone of thermal damage characterized by tissue coagulation left after the procedure, the physician must steadily hold the fiber a fixed distance (e.g., 1-2 mm) away from the tissue and slowly scan the beam over the target tissue without varying the distance. Clearly, the effectiveness and duration of this procedure is highly dependent on the skill of the treating physician and the use of a high-power laser.
While generally successful, none of these methods are adequate to treat all patients and all conditions. In particular, patients having severe tissue intrusion into the urethral lumen resulting from BPH or prostatic cancer are difficult to treat with minimally invasive protocols which rely on tissue shrinkage rather than resection. Additionally, those treatments which resect tissue often cause substantial bleeding which can be difficult to staunch. Thus, many of these patients will eventually require conventional surgical resection or follow-up procedures to stop bleeding.
For these reasons, it would be desirable to provide alternative and improved tissue-modifying systems which rely on the application of energy from one or more sources to the tissue. In particular, it would be desirable to provide minimally invasive methods and devices which provide for enlarging the luminal area and/or volumetric resection of tissue surrounding the urethra. It would be particularly desirable if such methods and devices were transurethrally introduced and provided for rapid removal or destruction of such tissues surrounding the urethra where the removal or destruction products can be removed from the lumen to relieve pressure on the urethra, even where large volumes of tissue are being removed. It would be particularly desirable if the methods and devices allowed for controllable tissue resection and/or ablation depth from very shallow depths to several millimeters or deeper. It would also be advantageous if the ablation could simultaneously cauterize treated tissue to limit bleeding. It would also be desirable if the depth of residual coagulated tissue that remains after tissue ablation were minimized or completely eliminated. It would be a further advantage if the use of a high-power laser were not required. It would be particularly beneficial if the methods and devices allowed for rapid and controlling tissue ablation or resection which is less dependent on skill of the treating physician. Methods and devices for performing such protocols should present minimal risk to the patient, should be relatively easy to perform by the treating physician, and should allow for alleviation of symptoms with minimal complications and side effects even in patients with severe disease. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
The use of water or other fluid jets as waveguides for carrying a laser beam for cutting and other manufacturing operations is described in U.S. Patent Application No. 2007/0278195, published Canadian application 2,330436 A1, PCT publication WO 99/56907, and U.S. Pat. Nos. 7,163,875; 5,902,499; and 5,773,791. U.S. Patent Application No. 2007/0025874 describes the use of laser fluid jets for disinfecting hands. The use of lasers for cutting biological tissue is described in U.S. Patent Application No. 2002/0128637 and for ablating prostate tissue is described in U.S. Pat. Nos. 5,257,991; 5,514,669; and 6,986,764. Use of a transurethral endoscope for bipolar radiofrequency prostate vaporization is described in Boffo et al. (2001) J. Endourol. 15:313-316. Pressurized water streams for effecting surgical incisions are described in U.S. Pat. Nos. 7,122,017 and 5,620,414, and for drilling teeth are described in U.S. Pat. No. 7,326,054. U.S. Pat. Nos. 5,785,521 and 6,607,524 describe the use of laser energy to cause thermo-elastic failure and fracture of hard biological materials combined with water/air technology to cool and remove (or further fracture) the already fractured material and debris from the treatment site. Radiofrequency discharge in saline solutions to produce tissue-ablative plasmas is discussed in Woloszko et al. (2002) IEEE Trans. Plasma Sci. 30:1376-1383 and Stalder et al. (2001) Appl. Phys. Lett. 79:4503-4505. Air/water jets for resecting tissue are described in Jian and Jiajun (2001) Trans. ASME 246-248. US2005/0288639 described a needle injector on a catheter based system which can be anchored in a urethra by a balloon in the bladder. U.S. Pat. Nos. 6,890,332; 6,821,275; and 6,413,256 each describe catheters for producing an RF plasma for tissue ablation. Other patents and published applications of interest include: U.S. Pat. Nos. 7,015,253; 6,953,461; 6,890,332; 6,821,275; 6,451,017; 6,413,256; 6,378,525; 6,296,639; 6,231,591; 6,217,860; 6,200,573; 6,179,831; 6,142,991; 6,022,860; 5,994,362; 5,872,150; 5,861,002; 5,817,649; 5,770,603; 5,753,641; 5,672,171; 5,630,794; 5,562,703; 5,322,503; 5,116,615; 4,760,071; 4,636,505; 4,461,283; 4,386,080; 4,377,584; 4,239,776; 4,220,735; 4,097,578; 3,875,229; 3,847,988; US2002/0040220; US2001/0048942; WO 93/15664; and WO 92/10142.